Is it possible to connect the wii u and a pc to the same external hard drive, I know you have to delete everything when connecting the wii u to the hard drive but can you then connect the pc without any trouble? Or do I have to have seperate extarnal disk drive for each?

It's possible, check this out: http://gbatemp.net/threads/can-you-make-a-wii-u-partition.337...
But honestly, you're better off just using a hard drive for your Wii U, and another one for your PC. For your Wii U, you'll probably never end up using more than 250 GB, but maybe you can get 500 GB just to be safe. I think 1 TB is a bit overkill for Wii U, but you can get them for like $5-$10 more so you can if you want to.

It's possible, but you have to partition the drive. Give it a WiiU format, and an NTFS/EXT format for PC, etc etc depending on how you want to use it. I don't recommend doing this though, due to possible performance issues. Just my two cents! I have a 2TB that I have on standby for when I need it for the WiiU.